The PMV / PPD thermal comfort calculator on this page implements the Fanger comfort model exactly as defined in ASHRAE Standard 55 and ISO 7730 — the two internationally recognised benchmarks for evaluating the thermal environment of occupied buildings. Rather than judging comfort from air temperature alone, the model performs a full heat balance on the human body using six variables and returns two indices: the Predicted Mean Vote (PMV), which places the average thermal sensation on a scale from −3 (cold) to +3 (hot), and the Predicted Percentage of Dissatisfied (PPD), which estimates how many occupants will be uncomfortable.
Figure 1 PMV PPD Calculation steps
For HVAC designers, building-performance researchers and CFD analysts, PMV/PPD is the standard post-processing metric that turns a temperature and velocity field into a defensible statement about occupant comfort. This calculator is validated against the worked cases in ISO 7730 Annex D, and it pairs naturally with the site's psychrometric calculator and HVAC load calculator.
1. The PMV / PPD Thermal Comfort Calculator
Enter the six comfort variables below. The tool solves the Fanger clothing-surface temperature iteratively and returns PMV, PPD, the comfort category and a position on the seven-point sensation scale. All computation runs in your browser; nothing is uploaded.
PMV / PPD Calculator (ASHRAE 55 / ISO 7730)
2. What PMV and PPD Actually Mean
The Predicted Mean Vote is the expected average of the thermal-sensation votes that a large panel of people would give on the ASHRAE seven-point scale. Professor P.O. Fanger derived it in the early 1970s from climate-chamber experiments with more than 1,300 subjects, combining their subjective votes with a steady-state energy balance of the human body.
| PMV | Thermal sensation |
|---|---|
| +3 | Hot |
| +2 | Warm |
| +1 | Slightly warm |
| 0 | Neutral |
| −1 | Slightly cool |
| −2 | Cool |
| −3 | Cold |
The Predicted Percentage of Dissatisfied converts PMV into the fraction of people likely to be unhappy. The relationship is symmetric about zero and — crucially — never reaches zero: even at a perfectly neutral PMV, PPD bottoms out at 5 %, because no single environment pleases everyone.
3. The Six Comfort Variables
PMV depends on four environmental and two personal variables. Omitting any one of them — the most common being mean radiant temperature — is the usual source of comfort mispredictions.
| Variable | Symbol | Typical indoor range | Type |
|---|---|---|---|
| Air temperature | ta | 18–30 °C | Environmental |
| Mean radiant temperature | tr | 18–30 °C | Environmental |
| Relative air speed | v | 0.0–1.0 m/s | Environmental |
| Relative humidity | RH | 30–70 % | Environmental |
| Metabolic rate | M | 1.0–2.0 met | Personal |
| Clothing insulation | Icl | 0.3–1.2 clo | Personal |
4. The Fanger Equations
PMV is the product of a sensitivity coefficient and the thermal load L — the difference between internal heat production and the heat the body actually loses to the environment:
The thermal load L collects six heat-loss terms: skin diffusion, sweat evaporation, latent and dry respiration, radiation and convection. The radiative and convective terms require the clothing-surface temperature tcl, which appears on both sides of its own balance and must be solved iteratively:
Once L is known, PPD follows in closed form:
The calculator above performs this iteration to a tolerance of 0.00015 and reproduces the worked answers in ISO 7730 Annex D (for example ta=tr=22 °C, v=0.1 m/s, RH=60 %, 1.2 met, 0.5 clo gives PMV = −0.75, PPD = 17 %).
5. How to Use It — 5 Steps
| # | Step | Detail |
|---|---|---|
| 1 | Enter the two temperatures | Air and mean radiant temperature in °C. If unknown, set tr = ta. |
| 2 | Enter air speed & humidity | Relative air speed (m/s) and RH (%). |
| 3 | Enter metabolic rate | Office work ≈ 1.1–1.2 met; standing ≈ 1.4 met. |
| 4 | Enter clothing insulation | Summer ≈ 0.5 clo; winter ≈ 1.0 clo. |
| 5 | Read PMV, PPD & category | Colour-coded verdict plus a marker on the sensation scale. |
6. Comfort Categories (ASHRAE 55 & ISO 7730)
| Category | PMV range | PPD limit | Typical application |
|---|---|---|---|
| A (ISO 7730) | −0.2 to +0.2 | < 6 % | High-expectation spaces (hospitals, premium offices) |
| B (ASHRAE 55) | −0.5 to +0.5 | < 10 % | Normal design target for offices and dwellings |
| C (ISO 7730) | −0.7 to +0.7 | < 15 % | Existing buildings, moderate expectation |
The recommended design target for most projects is Category B: keep PMV within ±0.5 and PPD will not exceed 10 %.
7. Worked Example
Consider a summer office: air temperature 26 °C, mean radiant temperature 26 °C, air speed 0.15 m/s, relative humidity 55 %, occupants doing light work (1.2 met) in light clothing (0.5 clo).
Entering these values, the calculator solves the clothing-surface temperature (tcl ≈ 30.4 °C) and returns:
The space sits right at the warm boundary of acceptable comfort. Two low-energy remedies are available without touching the air temperature: raising air speed toward 0.4 m/s (elevated-air-speed comfort, allowed by ASHRAE 55) or reducing the clothing assumption — both push PMV back toward neutral. This is exactly the kind of parametric study the calculator makes quick.
8. Using PMV as a CFD Post-Processing Field
In an indoor-airflow CFD simulation, PMV becomes a spatial field: at every cell you already have air temperature, air speed and (from a radiation model or a surface-temperature boundary) the radiant temperature. Feeding these into the Fanger model produces a PMV contour that reveals exactly where in the occupied zone comfort fails — under a diffuser, in a stagnant corner, beside a glazed façade.
This is a far more meaningful acceptance criterion than a single average temperature, and it is why comfort mapping is a standard deliverable in data-centre, atrium and cleanroom studies. If you are building the underlying airflow model, see the site's open-source CFD software round-up and the natural vs mechanical ventilation guide for boundary-condition context.
9. Frequently Asked Questions
What is PMV in thermal comfort?
PMV, the Predicted Mean Vote, is an index from the Fanger model that predicts the average thermal sensation of a large group on a seven-point scale from −3 (cold) through 0 (neutral) to +3 (hot). It comes from a heat balance of the body and depends on six variables: air temperature, mean radiant temperature, air speed, humidity, metabolic rate and clothing insulation.
What is PPD and how is it related to PMV?
PPD, the Predicted Percentage of Dissatisfied, estimates the share of occupants likely to be dissatisfied. It is computed directly from PMV. Even at a neutral PMV of 0, PPD is 5 %, because no single condition satisfies everyone.
What PMV range does ASHRAE 55 recommend?
ASHRAE 55 and ISO 7730 Category B recommend PMV between −0.5 and +0.5, corresponding to PPD ≤ 10 %. ISO 7730 also defines a stricter Category A (±0.2) and a relaxed Category C (±0.7).
What are the six factors that affect thermal comfort?
Four environmental (air temperature, mean radiant temperature, relative air speed, humidity) and two personal (metabolic rate, clothing insulation). All six enter the Fanger heat balance, which is why comfort cannot be judged from air temperature alone.
What is the difference between air temperature and mean radiant temperature?
Air temperature drives convective heat exchange with the body; mean radiant temperature is the area-weighted average of surrounding surface temperatures and drives radiant exchange. A room can have comfortable air temperature yet feel cold near a large cold window because the radiant temperature is low.
What are met and clo units?
The met is a metabolic-rate unit equal to 58.15 W/m² of body surface (a seated resting person). The clo is a clothing-insulation unit equal to 0.155 m²·K/W, where 1 clo is roughly a business suit. Both are inputs to the PMV model.
Author: Vikas Sharma, M.Tech (MNIT Jaipur). Educational tool implementing the ISO 7730 / ASHRAE 55 Fanger model, validated against ISO 7730 Annex D. Verify against the current published standards before use in formal building certification.